System for joining building boards

ABSTRACT

The invention relates to a system for laying and mechanically joining building panels, especially thin, hard, floating floors. Adjacent joint edges (3, 4) of two panels (1, 2) engage each other to provide a first mechanical connection locking the joint edges (3, 4) in a first direction (D1) perpendicular to the principal plane of the panels. In each joint, there is further provided a strip (6) which is integrated with one joint edge (3) and which projects behind the other joint edge (4). The strip (6) has an upwardly protruding locking element (8) engaging in a locking groove (14) in the rear side (16) of the other joint edge (4) to form a second mechanical connection locking the panels (1, 2) in a second direction (D2) parallel to the principal plane of the panels and at right angles to the joint. Both the first and the second mechanical connections allow mutual displacement of joined panels (1, 2) in the direction of the joint.

TECHNICAL FIELD

The invention generally relates to a system for providing a joint alongadjacent joint edges of two building panels, especially floor panels.

More specifically, the joint is of the type where the adjacent jointedges together form a first mechanical connection locking the jointedges to each other in a first direction at right angles to theprincipal plane of the panels, and where a locking device forms a secondmechanical connection locking the panels to each other in a seconddirection parallel to the principal plane and at right angles to thejoint edges, the locking device comprising a locking groove whichextends parallel to and spaced from the joint edge of one of the panels,and said locking groove being open at the rear side of this one panel.

The invention is especially well suited for use in joining floor panels,especially thin laminated floors. Thus, the following description of theprior art and of the objects and features of the invention will befocused on this field of use. It should however be emphasised that theinvention is useful also for joining ordinary wooden floors as well asother types of building panels, such as wall panels and roof slabs.

BACKGROUND OF THE INVENTION

A joint of the aforementioned type is known e.g. from SE 450,141. Thefirst mechanical connection is achieved by means of joint edges havingtongues and grooves. The locking device for the second mechanicalconnection comprises two oblique locking grooves, one in the rear sideof each panel, and a plurality of spaced-apart spring clips which aredistributed along the joint and the legs of which are pressed into thegrooves, and which are biased so as to tightly clamp the floor panelstogether. Such a joining technique is especially useful for joiningthick floor panels to form surfaces of a considerable expanse.

Thin floor panels of a thickness of about 7-10 mm, especially laminatedfloors, have in a short time taken a substantial share of the market.All thin floor panels employed are laid as "floating floors" withoutbeing attached to the supporting structure. As a rule, the dimension ofthe floor panels is 200×1200 mm, and their long and short sides areformed with tongues and grooves. Traditionally, the floor is assembledby applying glue in the groove and forcing the floor panels together.The tongue is then glued in the groove of the other panel. As a rule, alaminated floor consists of an upper decorative wear layer of laminatehaving a thickness of about 1 mm, an intermediate core of particle boardor other board, and a base layer to balance the construction. The corehas essentially poorer properties than the laminate, e.g. in respect ofhardness and water resistance, but it is nonetheless needed primarilyfor providing a groove and tongue for assemblage. This means that theoverall thickness must be at least about 7 mm. These known laminatedfloors using glued tongue-and-groove joints however suffer from severalinconveniences.

First, the requirement of an overall thickness of at least about 7 mmentails an undesirable restraint in connection with the laying of thefloor, since it is easier to cope with low thresholds when using thinfloor panels, and doors must often be adjusted in height to come clearof the floor laid. Moreover, manufacturing costs are directly linkedwith the consumption of material.

Second, the core must be made of moisture-absorbent material to permitusing water-based glues when laying the floor. Therefore, it is notpossible to make the floors thinner using so-called compact laminate,because of the absence of suitable gluing methods for suchnon-moisture-absorbent core materials.

Third, since the laminate layer of the laminated floors is highlywear-resistant, tool wear is a major problem when working the surface inconnection with the formation of the tongue.

Fourth, the strength of the joint, based on a glued tongue-and-grooveconnection, is restricted by the properties of the core and of the glueas well as by the depth and height of the groove. The laying quality isentirely dependent on the gluing. In the event of poor gluing, the jointwill open as a result of the tensile stresses which occur e.g. inconnection with a change in air humidity.

Fifth, laying a floor with glued tongue-and-groove joints istime-consuming, in that glue must be applied to every panel on both thelong and short sides thereof.

Sixth, it is not possible to disassemble a glued floor once laid,without having to break up the joints. Floor panels that have been takenup cannot therefore be used again. This is a drawback particularly inrental houses where the flat concerned must be put back into the initialstate of occupancy. Nor can damaged or worn-out panels be replacedwithout extensive efforts, which would be particularly desirable onpublic premises and other areas where parts of the floor are subjectedto great wear.

Seventh, known laminated floors are not suited for such use as involvesa considerable risk of moisture penetrating down into themoisture-sensitive core.

Eighth, present-day hard, floating floors require, prior to laying thefloor panels on hard subfloors, the laying of a separate underlay offloor board, felt, foam or the like, which is to damp impact sounds andto make the floor more pleasant to walk on. The placement of theunderlay is a complicated operation, since the underlay must be placedin edge-to-edge fashion. Different under-lays affect the properties ofthe floor.

There is thus a strongly-felt need to overcome the above-mentioneddrawbacks of the prior art. It is however not possible simply to use theknown joining technique with glued tongues and grooves for very thinfloors, e.g. with floor thicknesses of about 3 mm, since a joint basedon a tongue-and-groove connection would not be sufficiently strong andpractically impossible to produce for such thin floors. Nor are anyother known joining techniques usable for such thin floors. Anotherreason why the making of thin floors from e.g. compact laminate involvesproblems is the thickness tolerances of the panels, being about 0.2-0.3mm for a panel thickness of about 3 mm. A 3-mm compact laminate panelhaving such a thickness tolerance would have, if ground to uniformthickness on its rear side, an unsymmetrical design, entailing the riskof bulging. Moreover, if the panels have different thicknesses, thisalso means that the joint will be subjected to excessive load.

Nor is it possible to overcome the above-mentioned problems by usingdouble-adhesive tape or the like on the undersides of the panels, sincesuch a connection catches directly and does not allow for subsequentadjustment of the panels as is The case with ordinary gluing.

Using U-shaped clips of the type disclosed in the above-mentioned SE450,141, or similar techniques, to overcome the drawbacks discussedabove is no viable alternative either. Especially, biased clips of thistype cannot be used for joining panels of such a small thickness as 3mm. Normally, it is not possible to disassemble the floor panels withouthaving access to their undersides. This known technology relying onclips suffers from the additional drawbacks:

Subsequent adjustment of the panels in their longitudinal direction is acomplicated operation in connection with laying, since the clips urgethe panels tightly against each other.

Floor laying using clips is time-consuming.

This technique is usable only in those cases where the floor panels areresting on underlying joists with the clips placed therebetween. Forthin floors to be laid on a continuous, flat supporting structure, suchclips cannot be used.

The floor panels can be joined together only at their long sides. Noclip connection is provided on the short sides.

Technical Problems and Objects of the Invention

A main object of the invention therefore is to provide a system forjoining together building panels, especially floor panels for hard,floating floors, which allows using floor panels of a smaller overallthickness than present-day floor panels.

A particular object of the invention is to provide a panel-joiningsystem which

makes it possible in a simple, cheap and rational way to provide a jointbetween floor panels without requiring the use of glue, especially ajoint based primarily only on mechanical connections between the panels;

can be used for joining floor panels which have a smaller thickness thanpresent-day laminated floors and which have, because of the use of adifferent core material, superior properties than present-day floorseven at a thickness of 3 mm;

makes it possible between thin floor panels to provide a joint thateliminates any unevennesses in the joint because of thickness tolerancesof the panels;

allows joining all the edges of the panels;

reduces tool wear when manufacturing floor panels with hard surfacelayers;

allows repeated disassembly and reassembly of a floor previously laid,without causing damage to the panels, while ensuring high layingquality;

makes it possible to provide moisture-proof floors;

makes it possible to obviate the need of accurate, separate placement ofan underlay before laying the floor panels; and

considerably cuts the time for joining the panels.

These and other objects of the invention are achieved by means of apanel-joining system having the features recited in the appended claims.

Thus, the invention provides a system for making a joint along adjacentjoint edges of two building panels, especially floor panels, in whichjoint:

the adjacent joint edges together form a first mechanical connectionlocking the joint edges to each other in a first direction at rightangles to the principal plane of the panels, and

a locking device arranged on the rear side of the panels forms a secondmechanical connection locking the panels to each other in a seconddirection parallel to the principal plane and at right angles to thejoint edges, said locking device comprising a locking groove whichextends parallel to and spaced from the joint edge of one of saidpanels, termed groove panel, and which is open at the rear side of thegroove panel, said system being characterised in

that the locking device further comprises a strip integrated with theother of said panels, termed strip panel, said strip extendingthroughout substantially the entire length of the joint edge of thestrip panel and being provided with a locking element projecting fromthe strip, such that when the panels are joined together, the stripprojects on the rear side of the groove panel with its locking elementreceived in the locking groove of the groove panel,

that the panels, when joined together, can occupy a relative position insaid second direction where a play exists between the locking groove anda locking surface on the locking element that is facing the joint edgesand is operative in said second mechanical connection,

that the first and the second mechanical connection both allow mutualdisplacement of the panels in the direction of the joint edges, and

that the second mechanical connection is so conceived as to allow thelocking element to leave the locking groove if the groove panel isturned about its joint edge angularly away from the strip.

The term "rear side" as used above should be considered to comprise anyside of the panel located behind/underneath the front side of the panel.The opening plane of the locking groove of the groove panel can thus belocated at a distance from the rear surface of the panel resting on thesupporting structure. Moreover, the strip, which in the inventionextends throughout substantially the entire length of the joint edge ofthe strip panel, should be considered to encompass both the case wherethe strip is a continuous, uninterrupted element, and the case where the"strip" consists in its longitudinal direction of several parts,together covering the main portion of the joint edge.

It should also be noted (i) that it is the first and the secondmechanical connection as such that permit mutual displacement of thepanels in the direction of the joint edges, and that (ii) it is thesecond mechanical connection as such that permits the locking element toleave the locking groove if the groove panel is turned about its jointedge angularly away from the strip. Within the scope of the invention,there may thus exist means, such as glue and mechanical devices, thatcan counteract or prevent such displacement and/or upward angling.

The system according to the invention makes it possible to provideconcealed, precise locking of both the short and long sides of thepanels in hard, thin floors. The floor panels can be quickly andconveniently disassembled in the reverse order of laying without anyrisk of damage to the panels, ensuring at the same time a high layingquality. The panels can be assembled and disassembled much faster thanin present-day systems, and any damaged or worn-out panels can bereplaced by taking up and re-laying parts of the floor.

According to an especially preferred embodiment of the invention, asystem is provided which permits precise joining of thin floor panelshaving, for example, a thickness of the order of 3 mm and which at thesame time provides a tolerance-independent smooth top face at the joint.To this end, the strip is mounted in an equalising groove which iscountersunk in the rear side of the strip panel and which exhibits anexact, predetermined distance from its bottom to the front side of thestrip panel. The part of the strip projecting behind the groove panelengages a corresponding equalising groove, which is countersunk in therear side of the groove panel and which exhibits The same exact,predetermined distance from its bottom to the front side of the groovepanel. The thickness of the strip then is at least so great that therear side of the strip is flush with, and preferably projects slightlybelow the rear side of the panels. In this embodiment, the panels willalways rest, in the joint, with their equalising grooves on a strip.This levels out the tolerance and imparts the necessary strength to thejoint. The strip transmits horizontal and upwardly-directed forces tothe panels and down-wardly-directed forces to the existing subfloor.

Preferably, the strip may consist of a material which is flexible,resilient and strong, and can be sawn. A preferred strip material issheet aluminium. In an aluminium strip, sufficient strength can beachieved with a strip thickness of the order of 0.5 mm.

In order to permit taking up previously laid, joined floor panels in asimple way, a preferred embodiment of the invention is characterised inthat when the groove panel is pressed against the strip panel in thesecond direction and is turned anglularly away from the strip, themaximum distance between the axis of rotation of the groove panel andthe locking surface of the locking groove closest to the joint edges issuch that the locking element can leave the locking groove withoutcontacting the locking surface of the locking groove. Such a disassemblycan be achieved even if the aforementioned play between the lockinggroove and the locking surface is not greater than 0.2 mm.

According to the invention, the locking surface of the locking elementis able to provide a sufficient locking function even with very smallheights of the locking surface. Efficient locking of 3-mm floor panelscan be achieved with a locking surface that is as low as 2 mm. Even a0.5-mm-high locking surface may provide sufficient locking. The term"locking surface" as used herein relates to the part of the lockingelement engaging the locking groove to form the second mechanicalconnection.

For optimal function of the invention, the strip and the locking elementshould be formed on the strip panel with high precision. Especially, thelocking surface of the locking element should be located at an exactdistance from the joint edge of the strip panel.

Furthermore, the extent of the engagement in the floor panels should beminimised, since it reduces the floor strength.

By known manufacturing methods, it is possible to produce a strip with alocking pin, for example by extruding aluminium or plastics into asuitable section, which is thereafter glued to the floor panel or isinserted in special grooves. These and all other traditional methods dohowever not ensure optimum function and an optimum level of economy. Toproduce the joint system according to the invention, the strip issuitably formed from sheet aluminium, and is mechanically fixed to thestrip panel.

The laying of the panels can be performed by first placing the strippanel on the subfloor and then moving the groove panel with its longside up to the long side of the strip panel, at an angle between theprincipal plane of the groove panel and the subfloor. When the jointedges have been brought into engagement with each other to form thefirst mechanical connection, the groove panel is angled down so as toaccommodate the locking element in the locking groove.

Laying can also be performed by first placing both the strip panel andthe groove panel flat on the subfloor and then joining the panelsparallel to their principal planes while bending the strip downwardsuntil the locking element snaps up into the locking groove. This layingtechnique enables in particular mechanical locking of both the short andlong sides of the floor panels. For example, the long sides can bejoined together by using the first laying technique with downwardangling of the groove panel, while the short sides are subsequentlyjoined together by displacing the groove panel in its longitudinaldirection until its short side is pressed on and locked to the shortside of an adjacent panel in the same row.

In connection with their manufacture, the floor panels can be providedwith an underlay of e.g. floor board, foam or felt. The underlay shouldpreferably cover the strip such that the joint be%ween the underlays isoffset in relation to the joint between the floor panels.

The above and other features and advantages of the invention will appearfrom The appended claims and the following description of embodiments ofthe invention.

The invention will now be described in more detail hereinbelow withreference to the accompanying drawing Figures.

DESCRIPTION OF DRAWING FIGURES

FIGS. 1a and 1b schematically show in two stages how two floor panels ofdifferent thickness are joined together in floating fashion according toa first embodiment of the invention.

FIGS. 2a-c show in three stages a method for mechanically joining twofloor panels according to a second embodiment of the invention.

FIGS. 3a-c show in three stages another method for mechanically joiningthe floor panels of FIGS. 2a-c.

FIGS. 4a and 4b show a floor panel according to FIGS. 2a-c as seen frombelow and from above, respectively.

FIG. 5 illustrates in perspective a method for laying and joining floorpanels according to a third embodiment of the invention.

FIG. 6 shows in perspective and from below a first variant for mountinga strip on a floor panel.

FIG. 7 shows in section a second variant for mounting a strip on a floorpanel.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1a and 1b, to which reference is now made, illustrate a firstfloor panel 1, hereinafter termed strip panel, and a second floor panel2, hereinafter termed groove panel. The terms "strip panel" and "groovepanel" are merely intended to facilitate the description of theinvention, the panels 1, 2 normally being identical in practice. Thepanels 1 and 2 may be made from compact laminate and may have athickness of about 3 mm with a thickness tolerance of about ±0.2 mm.Considering this thickness tolerance, the panels 1, 2 are illustratedwith different Thicknesses (FIG. 1b), the strip panel 1 having a maximumthickness (3.2 mm) and the groove panel 2 having a minimum thickness(2.8 mm).

To enable mechanical joining of the panels 1, 2 at opposing joint edges,generally designated 3 and 4, respectively, the panels are provided withgrooves and strips as described in the following.

Reference is now made primarily to FIGS. 1a and 1b, and secondly toFIGS. 4a and 4b showing the basic design of the floor panels from belowand from above, respectively.

From the joint edge 3 of the strip panel 1, i.e. the one long side,projects horizontally a flat strip 6 mounted at the factory on theunderside of the strip panel 1 and extending throughout the entire jointedge 3. The strip 6, which is made of flexible, resilient sheetaluminium, can be fixed mechanically, by means of glue or in any othersuitable way. In FIGS. 1a and 1b, the strip 6 is glued, while in FIGS.4a and 4b it is mounted by means of a mechanical connection, which willbe described in more detail hereinbelow.

Other strip materials can be used, such as sheets of other metals, aswell as aluminium or plastics sections. Alternatively, the strip 6 maybe integrally formed with the strip panel 1. At any rate, the strip 6should be integrated with the strip panel 1, i.e. it should not bemounted on the strip panel 1 in connection with laying. As anon-restrictive example, the strip 6 may have a width of about 30 mm anda thickness of about 0.5 mm.

As appears from FIGS. 4a and 4b, a similar, although shorter strip 6' isprovided also at one short side 3' of the strip panel 1. The shorterstrip 6' does however not extend throughout the entire short side 3' butis otherwise identical with the strip 6 and, therefore, is not describedin more detail here.

The edge of the strip 6 facing away from the joint edge 3 is formed witha locking element 8 extended throughout The entire strip 6. The lockingelement 8 has a locking surface 10 facing the joint edge 3 and having aheight of e.g. 0.5 mm. The locking element 8 is so designed that whenthe floor is being laid and the strip panel 2 of FIG. 1a is pressed withits joint edge 4 against the joint edge 3 of the strip panel 1 and isangled down against the subfloor 12 according to FIG. 1b, it enters alocking groove 14 formed in the underside of the groove panel 2 andextending parallel to and spaced from the joint edge 4. In FIG. 1b, thelocking element 8 and the locking groove 14 together form a mechanicalconnection locking the panels 1, 2 to each other in the directiondesignated D2. More specifically, the locking surface 10 of the lockingelement 8 serves as a stop with respect to the surface of the lockinggroove 14 closest to the joint edge 4.

When the panels 1 and 2 are joined together, they can however occupysuch a relative position in the direction D2 that there is a small playΔ between the locking surface 10 and the locking groove 14. Thismechanical connection in the direction D2 allows mutual displacement ofthe panels 1, 2 in the direction of the joint, which considerablyfacilitates the laying and enables joining together the short sides bysnap action.

As appears from FIGS. 4a and 4b, each panel in the system has a strip 6at one long side 3 and a locking groove 14 at the other long side 4, aswell as a strip at one short side 3' and a locking groove 14' at theother short side 4'.

Furthermore, the joint edge 3 of the strip panel 1 has in its underside18 a recess 20 extending throughout the entire joint edge 3 and formingtogether with the upper face 22 of the strip 6 a laterally open recess24. The joint edge 4 of the groove panel 2 has in its top side 26 acorresponding recess 28 forming a locking tongue 30 to be accommodatedin the recess 24 so as to form a mechanical connection locking the jointedges 3, 4 to each other in the direction designated D1. This connectioncan be achieved with other designs of the joint edges 3, 4, for exampleby a bevel thereof such that the joint edge 4 of the groove panel 2passes obliquely in underneath the joint edge 3 of the strip panel 1 tobe locked between that edge and the strip 6.

The panels 1, 2 can be taken up in the reverse order of laying withoutcausing any damage to the joint, and be laid again.

The strip 6 is mounted in a tolerance-equalizing groove 40 in theunderside 18 of the strip panel 1 adjacent the joint edge 3. In thisembodiment, the width of the equalizing groove 40 is approximately equalto half the width of the strip 6, i.e. about 15 mm. By means of theequalizing groove 40, it is ensured that there will always exist betweenthe top side 21 of the panel 1 and the bottom of the groove 40 an exact,predetermined distance E which is slightly smaller than the minimumthickness (2.8 mm) of the floor panels 1, 2. The groove panel 2 has acorresponding tolerance-equalizing surface or groove 42 in the underside16 of the joint edge 4. The distance between the equalizing surface 42and the top side 26 of the groove panel 2 is equal to the aforementionedexact distance E. Further, the thickness of the strip 6 is so chosenthat the underside 44 of the strip is situated slightly below theundersides 18 and 16 of the floor panels 1 and 2, respectively. In thismanner, the entire joint will rest on the strip 6, and all verticaldownwardly-directed forces will be efficiently transmitted to thesubfloor 12 without any stresses being exerted on the joint edges 3, 4.Thanks to the provision of the equalizing grooves 40, 42, an entirelyeven joint will be achieved on the top side, despite the thicknesstolerances of the panels 1, 2, without having to perform any grinding orthe like across the whole panels. Especially, this obviates the risk ofdamage to the bottom layer of the compact laminate, which might giverise to bulging of the panels.

Reference is now made to the embodiment of FIGS. 2a-c showing in asuccession substantially the same laying method as in FIGS. 1a and 1b.The embodiment of FIGS. 2a-c primarily differs from the embodiment ofFIGS. 1a and 1b in that the strip 6 is mounted on the strip panel 1 bymeans of a mechanical connection instead of glue. To provide thismechanical connection, illustrated in more detail in FIG. 6, a groove 50is provided in the underside 18 of the strip panel 1 at a distance fromthe recess 24. The groove 50 may be formed either as a continuous grooveextending throughout the entire length of the panel 1, or as a number ofseparate grooves. The groove 50 defines, together with the recess 24, adovetail gripping edge 52, the underside of which exhibits an exactequalizing distance E to the top side 21 of the strip panel 1. Thealuminium strip 6 has a number of punched and bent tongues 54, as wellas one or more lips 56 which are bent round opposite sides of thegripping edge 52 in clamping engagement therewith. This connection isshown in detail from below in the perspective view of FIG. 6.

Alternatively, a mechanical connection between the strip 6 and the strippanel 1 can be provided as illustrated in FIG. 7 showing in section acut-away part of the strip panel 1 turned upside down. In FIG. 7, themechanical connection comprises a dovetail recess 58 in the underside 18of the strip panel 1, as well as tongues/lips 60 punched and bent fromthe strip 5 and clamping against opposing inner sides of the recess 58.

The embodiment of FIGS. 2a-c is further characterized in that thelocking element 8 of the strip 6 is designed as a component bent fromthe aluminium sheet and having an operative locking surface 10 extendingat right angles up from the front side 22 of the strip 6 through aheight of e.g. 0.5 mm, and a rounded guide surface 34 facilitating theinsertion of the locking element 8 into the locking groove 14 whenangling down the groove panel 2 towards The subfloor 12 (FIG. 2b), aswell as a portion 36 which is inclined towards the subfloor 12 and whichis not operative in the laying method illustrated in FIGS. 2a-c.

Further, it can be seen from FIGS. 2a-c that the joint edge 3 of thestrip panel 1 has a lower bevel 70 which cooperates during laying with acorresponding upper bevel 72 of the joint edge 4 of the groove panel 2,such that the panels 1 and 2 are forced to move vertically towards eachother when their joint edges 3, 4 are moved up to each other and thepanels are pressed together horizontally.

Preferably, the locking surface 10 is so located relative to the jointedge 3 that when the groove panel 2, starting from the joined positionin FIG. 2c, is pressed horizontally in the direction D2 against thestrip panel 1 and is turned angularly up from the strip 6, the maximumdistance between the axis of rotation A of the groove panel 2 and thelocking surface 10 of the locking groove is such that the lockingelement 8 can leave The locking groove 14 without coming into contactwith it.

FIGS. 3a-3b show another joining method for mechanically joiningtogether the floor panels of FIGS. 2a-c. The method illustrated in FIGS.3a-c relies on the fact that the strip 6 is resilient and is especiallyuseful for joining together the short sides of floor panels which havealready been joined along one long side as illustrated in FIGS. 2a-c.The method of FIGS. 3a-c is performed by first placing the two panels 1and 2 flat on the subfloor 12 and then moving them horizontally towardseach other according to FIG. 3b. The inclined portion 36 of the lockingelement 8 then serves as a guide surface which guides the joint edge 4of the groove panel 2 up on to the upper side 22 of the strip 6. Thestrip 6 will then be urged downwards while the locking element 8 issliding on the equalizing surface 42. When the joint edges 3, 4 havebeen brought into complete engagement with each other horizontally, thelocking element 8 will snap into the locking groove 14 (FIG. 3c),thereby providing the same locking as in FIG. 2c. The same lockingmethod can also be used by placing, in the initial position, the jointedge 4 of the groove panel with the equalizing groove 42 on the lockingelement 10 (FIG. 3a). The inclined portion 36 of the locking element 10then is not operative. This technique thus makes it possible to lock thefloor panels mechanically in all directions, and by repeating the layingoperations the whole floor can be laid without using any glue.

The invention is not restricted to the preferred embodiments describedabove and illustrated in the drawings, but several variants andmodifications thereof are conceivable within the scope of the appendedclaims. The strip 6 can be divided into small sections covering themajor part of the joint length. Further, the thickness of the strip 6may vary throughout its width. All strips, locking grooves, lockingelements and recesses are so dimensioned as to enable laying the floorpanels with flat top sides in a manner to rest on the strip 6 in thejoint. If the floor panels consist of compact laminate and if siliconeor any other sealing compound, a rubber strip or any other sealingdevice is applied prior to laying between the flat projecting part ofthe strip 6 and the groove panel 2 and/or in the recess 26, amoisture-proof floor is obtained.

As appears from FIG. 6, an underlay 46, e.g of floor board, foam orfelt, can be mounted on the underside of the panels during themanufacture thereof. In one embodiment, the underlay 45 covers the strip6 up to the locking element 8, such that the joint between the underlays46 becomes offset in relation to the joint between the joint edges 3 and4.

In the embodiment of FIG. 5, the strip 6 and its locking element 8 areintegrally formed with the strip panel 1, the projecting part of thestrip 6 thus forming an extension of the lower part of the joint edge 3.The locking function is the same as in the embodiments described above.On the underside 18 of the strip panel 1, there is provided a separatestrip, band or the like 74 extending throughout the entire length of thejoint and having, in this embodiment, a width covering approximately thesame surface as the separate strip 6 of the previous embodiments. Thestrip 74 can be provided in directly on the rear side 18 or in a recessformed therein (not shown), so that the distance from the front side 21,26 of the floor to the rear side 76, including the thickness of thestrip 74, always is at least equal to the corresponding distance in thepanel having the greatest thickness tolerance. The panels 1, 2 will thenrest, in the joint, on the strip 74 or only on the undersides 18, 16 ofthe panels, if these sides are made plane.

When using a material which does not permit downward bending of thestrip 6 or the locking element 8, laying can be performed in the wayshown in FIG. 5. A floor panel 2a is moved angled upwardly with its longside 4a into engagement with the long side 3 of a previously laid floorpanel 1 while at the same time a third floor panel 2b is moved with itsshort side 4b' into engagement with the short side 3a' of theupwardly-angled floor panel 2a and is fastened by angling the panel 2bdownwards. The panel 2b is then pushed along the short side 3a' of theupwardly-angled floor panel 2a until its long side 4b encounters thelong side 3 of The initially-laid panel 1. The two upwardly-angledpanels 2a and 2b are therefore angled down on to the subfloor 12 so asto bring about locking.

By a reverse procedure the panels can be taken up in The reverse orderof laying without causing any damage to the joint, and be laid again.

Several variants of preferred laying methods are conceivable. Forexample, the strip panel can be inserted under the groove panel, thusenabling the laying of panels in all four directions with respect to theinitial position.

What is claimed:
 1. A system for providing a joint between adjacentbuilding panels, comprising:each of said building panels including afirst edge and a second edge such that the first edge of each of saidbuilding panels forms a first mechanical connection with the second edgeof an adjacent one of the building panels locking the first and secondedges of the building panels to each other in a first direction at rightangles to a principal plane of the panels, and a locking device arrangedon a rear side of the building panels forming a second mechanicalconnection locking the building panels to each other in a seconddirection parallel to the principal plane and at right angles to thefirst and second edges, said locking device fitting within a lockinggroove extending parallel to and spaced apart from the first edge ofsaid building panels, and which locking groove is open at the rear sideof the building panels, the locking device comprising a strip integratedwith the second edge of each of said building panels, said stripextending throughout substantially an entire length of the second edgeand being provided with a locking element projecting from the strip,such that when two adjacent building panels are joined together, thestrip projects from the rear side of the second edge of the panels withits locking element received in the locking groove of an adjacentbuilding panel, the building panels, when joined together, can occupy arelative position in said second direction where a play exists betweenthe locking groove and a locking surface on the locking element that isfacing the first and second edges and is operative in said secondmechanical connection, the first and the second mechanical connectionsboth allow mutual displacement of the building panels in a direction ofthe first and second edges, and the second mechanical connection enablesthe locking element to leave the locking groove if the respectivebuilding panel is turned about its first edge angularly away from thestrip.
 2. A system as claimed in claim 1, wherein when the first edge ispressed against the second edge of the adjacent panel in said seconddirection and is turned angularly away from the strip, the maximumdistance between the axis of rotation of the first edge and the lockingsurface of the locking groove closest to the first and second edges issuch that the locking element can leave the locking groove withoutcontacting the locking surface of the locking groove.
 3. A system asclaimed in claim 1 wherein, the locking surface of the locking element(22) is extended from a front side (22) of the strip through a height insaid first direction that is less than or equal to 2 mm.
 4. A system asclaimed in claim 1, wherein the first mechanical connection is providedby the first edge engaging, in said first direction, between the secondedge of the adjacent panel and a front side of the strip.
 5. A system asclaimed in claim 1, wherein the strip is made of a material differentfrom that of the panel and fixedly mounted on the panel at the factory.6. A system as claimed in claim 5, wherein the strip (6), at least forone of the two panels, is received in a countersunk groove in the rearside of this one panel.
 7. A system as claimed in claim 5, whereinthestrip is mounted in an equalising groove which is countersunk in therear side of the panel and exhibits an exact, predetermined distancefrom its bottom to the front side of the panel, the part of the stripprojecting behind the adjacent panel engages a corresponding equalisinggroove which is countersunk in the rear side of the adjacent panel andwhich exhibits the same exact, predetermined distance from its bottom tothe front side of the adjacent panel, and the strip has at least such athickness that the rear side of the strip is flush with the rear sidesof the panels.
 8. A system as claimed in claim 7, wherein the strip hassuch a thickness that it is only partly received in the equalisinggrooves.
 9. A system as claimed in claim 5, wherein the strip is fixedto the strip panel by means of a mechanical connection.
 10. A system asclaimed in claim 9, wherein the mechanical connection between the stripand the panel comprises a gripping edge defined by two recesses in therear side of the panel, and tongues, lips or the like which are bent orpunched from the strip and which press against opposite outer sides ofthe gripping edge.
 11. A system as claimed in claim 9, wherein themechanical connection between the strip and the panel comprises a recessin the rear side of the panel, and tongues, lips or the like which arebent or punched from the strip and which press against opposing innersides of the recess.
 12. A system as claimed in claim 5, wherein thestrip is fixed to the panel by means of a binder.
 13. A system asclaimed in claim 5, wherein the strip is made of a flexible, preferablyresilient material, such as sheet aluminum.
 14. A system as claimed inclaim 1, wherein the locking element consists of a locking edge extendedcontinuously along the strip.
 15. A system as claimed in claim 1,wherein the locking element consists of a plurality of spaced-apartlocking elements distributed throughout the length of the strip.
 16. Asystem as claimed in claim 1, wherein the panels are rectangular andintended, at each of their four edges, to be joined to a similar panelby a first mechanical connection of the aforementioned type and a secondmechanical connection of the aforementioned type, each panel having afirst pair of first and second edges, one of which is provided with astrip of the aforementioned type and the other of which is provided witha locking groove of the aforementioned type, and a second pair ofopposite first and second edges, one of which is provided with a stripof the aforementioned type and the other of which is provided with alocking groove of the aforementioned type.
 17. A system as claimed inclaim 1, wherein an underlay of floor boards, foam, felt or the like isfixed to the rear sides of the panels.
 18. A system as claimed in claim17, wherein the underlay is fixed so as to cover the strip in saidsecond direction at least up to the locking element, such that a jointbetween the underlays of the two adjacent panels is offset in saidsecond direction relative to the first and second edges.
 19. A system asclaimed in any one of the preceding claims, wherein a sealing means,such as a sealing compound, a rubber strip or the like, is provided onthe front side of the strip between the locking element and the firstedge of the strip panel to seal against the adjacent panel.
 20. A systemas claimed in claim 2, wherein the locking surface of the lockingelement is extended from the front side of the strip through a height insaid first direction that is less than or equal to 2 mm.
 21. A systemfor providing a joint between adjacent building panels, comprising:eachof said building panels including a first edge and a second edge suchthat the first edge of each of said building panels forms a firstmechanical connection with the second edge of an adjacent one of thebuilding panels locking the first and second edges of the buildingpanels to each other in a first direction at right angles to a principalplane of the panels, and a locking device arranged on a rear side of thebuilding panels forming a second mechanical connection locking thebuilding panels to each other in a second direction parallel to theprincipal plane and at right angles to the first and second edges, saidlocking device fitting within a locking groove extending parallel to andspaced apart from the first edge of said building panels, and whichlocking groove is open at the rear side of the building panels, thelocking device comprising a strip integrally formed with the second edgeof each of said building panels, said strip extending throughoutsubstantially an entire length of the second edge and being providedwith a locking element projecting from the strip, such that when twoadjacent building panels are joined together, the strip projects fromthe rear side of the second edge of the panels with its locking elementreceived in the locking groove of an adjacent building panel, the firstand the second mechanical connections both allow mutual displacement ofthe building panels in a direction of the first and second edges, andthe second mechanical connection enables the locking element to leavethe locking groove if the respective building panel is turned about itsfirst edge angularly away from the strip.
 22. A system for providing ajoint between adjacent building panels, comprising:each of said buildingpanels including a first edge and a second edge such that the first edgeof each of said building panels forms a first mechanical connection withthe second edge of an adjacent one of the building panels locking thefirst and second edges of the building panels to each other in a firstdirection at right angles to a principal plane of the panels, and alocking device arranged on a rear side of the building panels forming asecond mechanical connection locking the building panels to each otherin a second direction parallel to the principal plane and at rightangles to the first and second edges, said locking device fitting withina locking groove extending parallel to and spaced apart from the firstedge of said building panels, and which locking groove is open at therear side of the building panels, the locking device comprising a stripintegrated with the second edge of each of said building panels, saidstrip extending throughout substantially an entire length of the secondedge and being provided with a locking element projecting from thestrip, such that when two adjacent building panels are joined together,the strip projects from the rear side of the second edge of the panelswith its locking element received in the locking groove of an adjacentbuilding panel, the first and the second mechanical connections bothallow mutual displacement of the building panels in a direction of thefirst and second edges, and the second mechanical connection enables thelocking element to leave the locking groove if the respective buildingpanel is turned about its first edge angularly away from the strip. 23.A system for providing a joint between adjacent building panels,comprising:each of said building panels including a first edge and asecond edge such that the first edge of each of said building panelsforms a first mechanical connection with the second edge of an adjacentone of the building panels locking the first and second edges of thebuilding panels to each other in a first direction at right angles to aprincipal plane of the panels, and a locking device arranged on a rearside of the building panels forming a second mechanical connectionlocking the building panels to each other in a second direction parallelto the principal plane and at right angles to the first and secondedges, said locking device fitting within a locking groove extendingparallel to and spaced apart from the first edge of said buildingpanels, and which locking groove is open at the rear side of thebuilding panels, the locking device comprising a strip integrated withthe second edge of each of said building panels, said strip beingprovided with a locking element projecting from the strip, such thatwhen two adjacent building panels are joined together, the stripprojects from the rear side of the second edge of the panels with itslocking element received in the locking groove of an adjacent buildingpanel, the first and the second mechanical connections both allow mutualdisplacement of the building panels in a direction of the first andsecond edges, and the second mechanical connection enables the lockingelement to leave the locking groove if the respective building panel isturned about its first edge angularly away from the strip; wherein thestrip is mounted in an equalizing groove which is countersunk in therear side of each of the building panels and exhibits an exact,predetermined distance from its bottom to the front side of the panel,the part of the strip projecting behind the adjacent panel engages acorresponding equalising groove which is countersunk in the rear side ofthe adjacent panel and which exhibits the same exact, predetermineddistance from its bottom to the front side of the adjacent panel, andthe strip has at least such a thickness that the rear side of the stripis flush with the rear sides of the panels.